From 248941a0f4b4792b6935546da1c1e6bdda61846e Mon Sep 17 00:00:00 2001
From: Fabian Vogt <fabian@ritter-vogt.de>
Date: Thu, 11 Jan 2018 22:07:45 +0100
Subject: Fix KFilePreviewGenerator::LayoutBlocker

Summary:
QAbstractItemViews does layout in a timer event handler to avoid unnecessary
layout calculations. Changes which cause a relayout only start the timer.
LayoutBlocker has the restriction that it only works if the event loop is not
entered during its lifetime. Without an event loop there's no expensive
relayout anyway, making the LayoutBlocker pointless in such cases.
LayoutBlocker works by changing the uniformItemSizes property of the QListView
to true and in the destructor back to the original value again. Those changes
do not trigger a relayout in QListView, so if the QListView did a layout with
uniformItemSizes set to true, it stays that way.
Fix it by triggering a relayout in ~LayoutBlocker.

This got exposed by a change in Qt, which results in QListView doing a relayout
while the LayoutBlocker is active.

BUG: 352776

Test Plan: kfilewidgettest_gui has proper item sizes now.

Reviewers: #frameworks, dfaure

Reviewed By: dfaure

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D9830
---
 src/filewidgets/kfilepreviewgenerator.cpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/filewidgets/kfilepreviewgenerator.cpp b/src/filewidgets/kfilepreviewgenerator.cpp
index 7965ab8..15b8ab8 100644
--- a/src/filewidgets/kfilepreviewgenerator.cpp
+++ b/src/filewidgets/kfilepreviewgenerator.cpp
@@ -70,10 +70,7 @@
  *
  * QListView does not invoke QItemDelegate::sizeHint() when the
  * uniformItemSize property has been set to true, so this property is
- * set before exchanging a block of icons. It is important to reset
- * it again before the event loop is entered, otherwise QListView
- * would not get the correct size hints after dispatching the layoutChanged()
- * signal.
+ * set before exchanging a block of icons.
  */
 class KFilePreviewGenerator::LayoutBlocker
 {
@@ -92,6 +89,11 @@ public:
     {
         if (m_view != nullptr) {
             m_view->setUniformItemSizes(m_uniformSizes);
+            /* The QListView did the layout with uniform item
+             * sizes, so trigger a relayout with the expected sizes. */
+            if (!m_uniformSizes) {
+                m_view->setGridSize(m_view->gridSize());
+            }
         }
     }
 
-- 
cgit v0.11.2

